Chili with Polenta and Vegetables

In a pot, bring milk and 2 1/2 cups water to a simmer; season lightly with salt. Whisking constantly, add polenta in a thin stream. Reduce heat to low; cook, whisking occasionally, until polenta is tender and creamy, about 5 minutes. Remove from heat; stir in butter. Season with salt and pepper; cover to keep warm.

In a large skillet over medium-high, heat oil and garlic until fragrant, 1 to 2 minutes. Remove and discard garlic; add mushrooms and cook, stirring, until browned, 10 to 12 minutes. Add spinach; season with salt and pepper, and cook until just wilted, 1 to 2 minutes. Add vinegar; cook 30 seconds. Season with salt and pepper.

Reheat chili. Serve with vegetables over polenta.